1. Field of the Invention
The present invention relates to surgical instruments for withdrawing fluid from or introducing fluids into a cavity of the body. The present invention more particularly relates to double lumen hemodialysis catheters and assemblies incorporating the catheters.
2. State of the Art
Hemodialysis catheters are catheters used to access blood for performing hemodialysis. The distal end of the catheter is inserted into an artery or vein of a patient, and the proximal end of the catheter is connected to a hemodialysis mechanism which causes the blood to flow through a hemodialysis membrane which filters the blood. The blood is then forwarded back to the proximal end of the catheter and then through the catheter and back into the artery or vein. The hemodialysis catheter must therefore have at least two lumens; one for the removal of blood; and the other for the return of the blood into the body. Pumps coupled to the hemodialysis mechanism are typically utilized for causing the blood to flow through the circuitous path.
Many types of hemodialysis catheter assemblies are known in the art. Examples of such catheter assemblies are seen in U.S. Pat. Nos. 4,314,402, 4,692,141, and 4,895,561 to Mahurkar. A representation of a similar catheter assembly is seen in prior art FIGS. 1 and 1a hereof. In particular, the hemodialysis catheter assembly 10 of FIGS. 1 and 1a is comprised of a double "D" cannula 12 (see FIG. 1a) with proximal and distal ends, a Y connector 14 coupled to the proximal end of the cannula 12, two flexible extenders 16a, 16b which coupled to the Y connector 14 and terminate in male luer slips or locks 18a, 18b, and two pinch stopcocks 20a, 20b which are used to pinch off the flexible extenders 16a and 16b when blood flow is not desired. Typically, a wing attachment device 22 is provided toward the proximal end of the cannula 12. The wing attachment device 22 is provided with holes 23 so that the wing attachment device 22 and hence the catheter 12 may be sutured to the skin of the patient.
As may be seen by close examination of prior art FIGS. 1 and 1a, the cannula 12 is a double D extrusion having an outlet lumen 12a and an inlet lumen 12b. The outlet lumen 12a of cannula 12 typically has a distal opening 24a, and sometimes includes side holes 25a. Likewise, the inlet lumen 12b of cannula 12 has side openings or ports 25b. Typically, blood is pumped from a vein through holes 25b into lumen 12b of catheter 12, and then through the Y connector 14, extender 16b, luer 18b and into the dialyzer (not shown) where the blood is filtered. The filtered blood is returned through luer 18a, extender 16a, Y connector 14 into lumen 12a of catheter 12 and out through opening 24a and holes 25a.
While the hemodialysis catheter assemblies of the art are extremely useful for patients who must undergo regular treatments, they still suffer from various drawbacks. First, the pincers which are used as valve means are unsightly, cumbersome, and uncomfortable to the patient, and most particularly so when used in the jugular vein of the neck. Second, the double D configuration of the catheter allows blood to be sucked from only one side of the catheter. If the catheter happens to be flush against the wall of a blood vessel with the suction hole against the wall, then blood will not easily flow into the catheter. Third, with the catheter configuration of the prior art, when blood is expelled from the tip of the catheter, it must be through a narrow opening. If a side hole, such as shown in prior art FIG. 1a is used to increase the outflow, the outflow through the side hole further pushes the cannula against the wall of the vessel and prevents inflow. Fourth, the materials used in the prior art hemodialysis catheters have dictated that the hemodialysis catheters be replaced periodically because the materials in contact with the skin either disintegrate or because the tissue may degrade the material or the entry site though the skin may become infected. Also, the tips of the prior art hemodialysis catheters tend to be relatively hard and sharp and often tend to traumatize the blood vessels during insertion and manipulation. Fifth, the hemodialysis catheters of the prior art tend to clog with coagulations (clots) of blood between uses. In order to dissolve or remove the clots, heparin flushes are required. However, not only do the heparin flushes require the time of a skilled practitioner, but they are not always effective.